Your last checkup put your A1C in the prediabetes range, and a coworker swears that NMN capsules, or the related supplement nicotinamide riboside (NR), “fixed” her blood sugar. Both are sold as boosters of NAD+, a molecule cells use to turn food into energy. Before you add a bottle to the cart, it is worth asking what happened when researchers measured blood sugar control directly in people.
So far, controlled trials say these supplements have not lowered the numbers your doctor tracks. One small study in women with prediabetes found that muscle handled insulin better after NMN, but fasting glucose and A1C did not change. A careful NR trial in men with obesity found no improvement at all, and a pooled review of eight NMN trials found no effect on fasting glucose, insulin or A1C.
The NMN study that made headlines
In 2021, Washington University researchers reported in Science on 25 postmenopausal women who were overweight or obese and had prediabetes. For 10 weeks, 13 took NMN and 12 took a placebo, without knowing which. The team used the hyperinsulinemic-euglycemic clamp, a demanding hospital test that measures how fast the body clears sugar from the blood under a steady insulin infusion.
Insulin-driven sugar uptake into muscle rose about 25 percent in the NMN group and did not change on placebo. The authors noted that this was similar in size to what is seen after losing around 10 percent of body weight. But almost everything else stayed put: body fat, liver fat, blood pressure, fasting glucose, fasting insulin and A1C. Liver and fat tissue insulin sensitivity did not improve either. Two of the researchers held patent interests related to NMN.
Nicotinamide riboside and the pooled NMN trials
A Danish team ran a 12-week randomized, placebo-controlled trial of NR in 40 sedentary men aged 40 to 70 with obesity and insulin resistance, reported in 2018 in the American Journal of Clinical Nutrition. Using the same clamp method, they found that insulin sensitivity, the liver’s sugar output, and sugar disposal did not improve. Body composition and fat burning did not change. NR appeared safe over the 12 weeks.
A follow-up paper from the same trial in 2019 looked at oral glucose tolerance tests and the pancreas. Fasting and after-drink glucose, insulin, C-peptide and gut hormones such as GLP-1 were unchanged, and insulin-producing cell function did not respond.
A 2024 systematic review in Current Diabetes Reports combined eight randomized NMN trials published from 2021 to 2023, with 342 mostly middle-aged and older adults, most without diabetes. Lasting from two weeks to 12 weeks, the trials showed no significant benefit on fasting glucose, fasting insulin, A1C, an insulin resistance score, or cholesterol and triglycerides. The authors cautioned that the trials were small and short.
What does lower diabetes risk
The Diabetes Prevention Program, described by the National Institute of Diabetes and Digestive and Kidney Diseases, gives a sharp contrast. In adults at high risk, a structured lifestyle program aiming for 7 percent weight loss and 150 minutes of activity a week cut the chance of developing type 2 diabetes by 58 percent over about three years. The drug metformin cut it by 31 percent.
So a practical takeaway: if you have prediabetes, an NAD+ booster is not a proven way to bring your A1C down. Ask your clinician about a recognized lifestyle change program, and if you still want to try a supplement, tell them so it can be tracked against your next lab results. Research-grade NAD+ products sold for laboratory use were not the products tested in these trials and carry no evidence of their own for blood sugar. Not medical advice.
Sources
- Yoshino M et al. Nicotinamide mononucleotide increases muscle insulin sensitivity in prediabetic women. Science, 2021 (PubMed)
- Dollerup OL et al. A randomized placebo-controlled clinical trial of nicotinamide riboside in obese men: safety, insulin-sensitivity, and lipid-mobilizing effects. Am J Clin Nutr, 2018 (PubMed)
- Dollerup OL et al. Effects of nicotinamide riboside on endocrine pancreatic function and incretin hormones in nondiabetic men with obesity. J Clin Endocrinol Metab, 2019 (PubMed)
- Chen F et al. Effects of nicotinamide mononucleotide on glucose and lipid metabolism in adults: a systematic review and meta-analysis of randomised controlled trials. Curr Diab Rep, 2024 (PubMed)
- NIDDK: Diabetes Prevention Program (DPP)
Related reading
- NMN for Older Legs: Four Small Trials on Walking Speed and Grip
- Walking for Blood Pressure? Adding Nicotinamide Riboside Did Not Help More
- NAD Precursors Can Raise Blood Markers Without Proving Anti-Aging
By The Everyday Brief. AI-assisted drafting with automated source and editorial checks. Sources fetched 2026-10-24 PT. Not medical advice.